Joint WLAN Power and Rate Control to Mitigate Co-Located LTE TDD Interference

ABSTRACT

In some implementations, a method of a wireless local area network (WLAN) transmitter includes, in response to interference with a long term evolution (LTE) receiver, determining a de-sense value of the LTE receiver; determining a transmission rate for the WLAN transmitter, the transmission rate requiring an equal or lower receiver sensitivity than a received signal strength threshold; determining a frame aggregation size based on the transmission rate and an LTE frame configuration for the LTE receiver; determining a transmission power based on the de-sense value; and transmitting data during a downlink receiving period of the LTE receiver using the transmission rate, the frame aggregation size, and the transmission power.

FIELD

This disclosure relates to interference management for Long TermEvolution (LTE) and wireless local area network (WLAN, also known as“WiFi”) systems.

BACKGROUND

Multiple wireless communication networks (e.g., cellular network, WLANnetwork, Bluetooth network, etc.) can be co-located. The multiplecommunication networks can provide services to user devices located inrespective serving areas. In some instances, a user device can receiveservices from and access to two or more communication networks when thedevice is located within the coverage areas of the two or morecommunication systems. As an example, a mobile device located inside orin the vicinity of a building may receive both cellular coverage of anLTE network and WiFi coverage of a WLAN network installed in thebuilding. The user device can establish phone calls via the LTE networkand access the Internet via the WLAN network or the LTE network. Inother cases, some services will be tied to a particular network (e.g.private network, or a carrier app store, etc . . . ).

DESCRIPTION OF DRAWINGS

FIG. 1 is an example wireless communication system.

FIG. 2 is a schematic illustrating an example network node.

FIG. 3 is a schematic illustrating an example user-equipment device.

FIG. 4 is a flowchart illustrating an example process for transmissionpower and rate control of a WLAN transmitter.

FIG. 5 is a plot illustrating example transmission efficiencies versusdifferent frame aggregation sizes.

DETAILED DESCRIPTION

The present disclosure is directed to interference management tomitigate interference between WLAN and LTE systems. For example, exampletechniques and systems are disclosed to jointly control transmissionpower and rate of a WLAN transmitter to mitigate inference to co-locatedLTE TDD systems. In some instances, some of the LTE time division duplex(TDD) bands (e.g. B40, B41) have limited or no guard band with the ISM2.4 GHz band that can be used by the WLAN system. Depending on the LTEtransmission (TX) power spectral density, some LTE transmissions may jamthe WLAN receiver partially or completely and prevent the reception ofWLAN downlink (DL) traffic. On the other hand, depending on the WLANtransmit power and the frame duration, the WLAN transmissions may jamthe LTE receiver. To minimize the probability of both radios jammingeach other, some implementations silence the WLAN radio during LTEreceiving (RX) periods and only allow operation of the LTE radio. Insome other implementations, concurrent operations of the WLAN and LTEradios can be achieved. Example techniques and systems are disclosed forjoint WLAN TX power and rate control with awareness of the LTE-TDD frameconfiguration. The example techniques and systems can reduce or preventperformance degradation due to suspending WLAN operation and allowconcurrent operation of LTE and WLAN transceivers without LTE RXde-sensing.

In some implementations, transmission power of the WLAN transmitter canbe reduced to reduce interference to the LTE receiver, thus reducing orminimizing the de-sensing of the LTE receiver. For example, a de-sensevalue of the LTE receiver can be identified. The reduced (or new) WLANtransmission power can be a regular (or current) WLAN TX power (e.g.,during normal WLAN transmission without concurrent operations with theLTE transceiver) minus the de-sense value of the LTE receiver. The WLANTX power reduction can cause a decrease insignal-to-interference-plus-noise ratio (SINR) at the WLAN receiver. Forinstance, the received signal strength at the WLAN receiver may be theregular received signal strength (e.g., corresponding to the regularWLAN TX power) minus the de-sense value of the LTE receiver. The WLAN TXpower and received signal strength can be determined in another mannerand can depend on additional or different factors.

To accommodate the SINR decrease at the WLAN receiver, the WLANtransmitter can select lower, more resilient, physical layer (PHY) datarate (or transmission rate).

In some instances, for certain LTE TDD frame configurations, higher WLANthroughput is achievable by using continuous WLAN operation at lowerdata rates than intermittent WLAN operation at high data rate.

The example techniques can identify the highest WLAN uplink (UL) datarate that can ensure proper operation at the WLAN receiver withavailable SINR while allowing for concurrent LTE-TDD and WLANoperations. In some instances, the highest WLAN UL data rate allowingfor concurrent operation is selected for transmission, instead ofaggressively selecting the lowest possible WLAN data rate (e.g. 6 Mbps).For example, a (new) WLAN UL data rate can be selected such that itrequires an equal or less receiver sensitivity than a received signalstrength threshold. The received signal strength threshold can be basedon, for example, the received signal strength using the reduced WLAN TXpower that takes into account the LTE receiver de-sensing. As oneexample, the received signal strength threshold can be the regularreceived signal strength minus the de-sense value of the LTE receiver.As another example, the received signal strength threshold can be areceiver sensitivity (e.g., corresponding to using a regular (orcurrent) WLAN data rate with the regular WLAN TX power) minus thede-sense value of the LTE receiver. The received signal strengththreshold can be determined in another manner and can be based onadditional or different factors.

In some implementations, the example techniques take into considerationframe aggregation (e.g., Aggregation of MAC protocol data units(A-MPDU)) that is available in IEEE 802.11n and 802.11ac. The exampletechniques examine the impact of a well behaved interferer such as LTETDD on IEEE 802.11n aggregation. For example, a maximum frameaggregation size for UL WLAN data transmission can be determined. Insome implementations, the maximum frame aggregation size can bedetermined such that an aggregated WLAN frame with the maximum frameaggregation size can fit within a LTE TDD frame or one or moresubframes. For instance, a maximum frame aggregation size using theregular (or current) WLAN data rate with the regular WLAN TX power canbe determined such that the corresponding aggregated WLAN frame has atransmission duration less than or equal to the LTE transmission period(e.g., during one or more LTE TDD UL subframes). In another example, amaximum frame aggregation size using the new WLAN data rate with thereduced (or new) WLAN TX power can be determined such that thecorresponding WLAN frame has a transmission duration less than or equalto the whole LTE transmission period (e.g., includes both LTE TDD ULsubframes and DL subframes). The maximum frame aggregation size candepend on device capability (e.g., available buffers) or other factors.

In some implementations, given a determined frame aggregation size,corresponding transmission efficiency and throughput can be determined.For example, a regular throughput for the WLAN transmitter (e.g.,without concurrent WLAN and LTE operations) can be based on a product ofthe regular WLAN data rate and the efficiency determined based on theframe aggregation size of the regular WLAN data rate. Similarly, a newthroughput for the WLAN transmitter with concurrent WLAN and LTEoperations can be based on a product of the new WLAN data rate and theefficiency determined based on the frame aggregation size of the newWLAN data rate. The regular throughput and the new throughput can becompared. The WLAN transmitter can use the new data rate, the newtransmission power, and the corresponding frame aggregation size fordata transmission during LTE receiving period if the new throughput isequal to or larger than the regular throughput. Otherwise, the WLANtransmitter can use the regular data rate, the regular transmissionpower, and the corresponding frame aggregation size for datatransmission during LTE UL transmitting period.

In some implementations, the frame aggregation size can be determinedbased on 3-wire (LTE_TX, LTE_RX, WLAN_PRIO). LTE_TX indicates thebeginning of LTE_TX (it could be slightly offset from the actualtransmission event to given enough time for WLAN to change itsbehaviour. In some implementations, the assertion of this line may bequalified/filtered such that it is only asserted if there is a highprobability that the impending LTE TX will indeed interfere withoccurring/expected WLAN RX). LTE_RX is similar to LTE_TX but for LTEreceptions. For WLAN_PRIO, usually WLAN is assumed to be of lowerpriority and it may be gracefully or abruptly silenced. However, someWLAN traffic (e.g. Beacons) need to be received/transmitted else theWLAN connection may be lost (i.e. compared to say a degradation in WLANTP). Protecting this kind of crucial traffic may take precedence overregular LTE traffic. The presence of such traffic is indicated by theWLAN_PRIO line. Now, if the WLAN is trying to abuse this line (e.g.,assert it all the time), then the LTE may start to ignore or only honora certain number of requests. In some other implementations, the exampletechniques can make use of the LTE TDD frame configuration exchangedover the Bluetooth Special Interest Group (SIG) (BT-Sig) 2 interfaceinstead of relying on the 3-wire (LTE_TX, LTE_RX, WLAN_PRIO) fordetermining proper frame aggregation size for WLAN transmission. Theexample techniques and systems described in this disclosure may provideadditional or different advantages.

FIG. 1 is an example wireless communication system 100. As illustrated,the wireless communication system 100 includes a cellular network 120and a WLAN network 130. The cellular network 120 and the WLAN network130 may communicate based on orthogonal frequency division multiplexing(OFDM), orthogonal frequency division multiple access (OFDMA),space-division multiplexing (SDM), frequency-division multiplexing(FDM), time-division multiplexing (TDM), code division multiplexing(CDM), or others. Communications within the cellular network 120 may betransmitted in accordance with Long Term Evolution (LTE), Global Systemfor Mobile Communication (GSM) protocols, Code Division Multiple Access(CDMA) protocols, Universal Mobile Telecommunications System (UMTS),Unlicensed Mobile Access (UMA), or others.

The wireless communication system 100 can include one or more networknodes (e.g., 105 and 125) and one or more user equipment (UE, e.g., 110a and 110 b). The network nodes may take several forms in a mobilecommunication system, such as (but not limited to) an evolved Node B(eNB), a base station, a Node B, a wireless access point, a radionetwork controller, a base transceiver station, a layer two relay node,a layer three relay node, a femto cell, home eNB (HeNB), a home Node B(HNB), a base station controller, or other network node that includesradio resource control (RRC). In the illustrated example, the cellularnetwork 120 can be an LTE network and the network node 105 can be aneNB. The network node 125 of the WLAN network 130 can be a wirelessaccess point (AP). The wireless communication system and its componentscan be different in another implementation.

In some implementations, the wireless communication system 100 can alsoinclude one or more 2G/3G systems based on, for example, a Global Systemfor Mobile communication (GSM), Interim Standard 95 (IS-95), UniversalMobile Telecommunications System (UMTS), or a CDMA2000 (Code DivisionMultiple Access). The cellular network 120 is connected to core networkcomponents 150. In some implementations, the cellular network 120 andthe core network components 150 can include one or more radio accessnetworks (e.g., an evolved-UMTS terrestrial radio access networks(E-UTRAN)), core networks (e.g., evolved packet cores (EPCs)), orexternal networks (e.g., IP networks).

The cellular network 120 can support and implement LTE standard andserve one or more user equipment (e.g., UEs 110 a and 110 b) within itscoverage range (also known as coverage area, service area, etc.). Forexample, the cell 122 may represent the coverage area of eNB 105. UEs110 a and 110 b are located within in the cell 122 and are served by eNB105. The UEs 110 a and 110 b may be any electronic device used by anend-user to communicate, for example, within the wireless communicationsystem 100. The UEs may transmit voice data, video data, user data,application data, multimedia data, text, web content and/or any othercontent.

In some implementations, the UES 110 a and 110 b and the eNB 105 canoperate under a time-division duplexing (TDD) or a frequency-divisionduplexing (FDD) mode. Depending on the operating mode and standard,different radio resources (e.g., frequency bands) can be allocated forcommunications between a network node and UE. For instance, Table 1shows an example frequency allocation for TDD LTE. For example, spectrumaround 1.9 GHz, 2.3-2.7 GHz, and 3.5 GHz can be assigned to TDD LTE. Theassigned spectrum can be further divided into multiple frequency bands(or sub-bands) and each band can have a respective bandwidth and centralfrequency occupying a respective radio frequency range. For example,Bands 40 and 41 are allocated with spectrum around 2.4 GHz. The radiofrequency resources can be allocated similarly or differently foranother operating mode (e.g., FDD mode) or another communicationstandard (e.g., 2G, 3G, or 4G standard).

TABLE 1 TDD LTE Frequency Bands and Frequencies LTE BAND ALLOCATIONWIDTH OF NUMBER (MHZ) BAND (MHZ) 33 1900-1920 20 34 2010-2025 15 351850-1910 60 36 1930-1990 60 37 1910-1930 20 38 2570-2620 50 391880-1920 40 40 2300-2400 100 41 2496-2690 194 42 3400-3600 200 433600-3800 200

The WLAN network 130 can support and implement IEEE 802.11 standards(e.g., IEEE 802.11a, b, g, n, ac, ad, af) and provide network access toa wireless device (e.g., UE 110 b) within its coverage range. The AP 125serves as the network node of the WLAN 130 that allows the wirelessdevice (e.g., UE 110 b) to access to, for example, other wired orwireless network (e.g., Internet). Depending on the supported standard,the WLAN network 130 can use, for example, 2.4 GHz, 3.7 GHz, 5 GHz, 60GHz frequency bands. For instance, IEEE 802.11b, 802.11g, 802. 11nstandards specify 2.4 GHz ISM band. The WLAN network 130 supporting IEEE802.11b/g/n can use 2.4 GHz ISM band for transmission.

As illustrated in the FIG. 1, the LTE network 120 and the WLAN network130 can be co-located and can have overlapping coverage area. UE (e.g.,UE 110 b) located in the overlapping coverage area of the cellularnetwork 120 and the WLAN network 130 can access to and receive servicesfrom both networks. The UE 110 b can include an LTE transceiver 112 anda WLAN transceiver 114 for transmission based on LTE and WLAN protocols,respectively. The two transceivers 112 and 114 can be connected via oneor more interfaces 116. The interfaces can be, for example, BT-Sig 2interface, or other appropriate interfaces.

Although FIG. 1 shows the two transceivers 112 and 114 as separatedmodules, in some implementations, they can be integrated together orthey can share some or all hardware or software components. In someimplementations, each transceiver (or radio) can include a transmitter,a receiver, and other appropriate circuitry or components. For example,the LTE transceiver can include an LTE transmitter and an LTE receiverthat are configured to transmit and receive data based on the LTEstandard, for example, in TDD or FDD mode. Similarly, a WLAN transceivercan include a WLAN transmitter and a WLAN receiver that are configuredto transmit and receive data based on the WLAN standard (e.g., IEEE802.11n).

In some instances, the LTE network 120 and the WLAN network 130 can bothoperate on or near 2.4 GHz ISM band and may cause interference to eachother. For example, the WLAN receiver of the UE 110 b may receiveinterference from the LTE transmitter of the UE 110 b; and the LTEreceiver of the UE 110 b may receive interference from the WLANtransmitter of the UE 110 b. In some implementations, the UE 110 b canhave concurrent operations of the LTE transceiver 112 and WLANtransceiver 114 without silencing one transmitter to protect receptionof another receiver, for example, based on example techniques describedwith respect to FIG. 4, or another technique.

In general, the UE 110 a or 110 b may be referred to as mobileelectronic device, user device, mobile station, subscriber station,portable electronic device, mobile communications device, wirelessmodem, or wireless terminal. The term “UE” can also refer to anyhardware or software component that can terminate a communicationsession for a user. In addition, the terms “user equipment,” “UE,” “userequipment device,” “user agent,” “UA,” “user device,” and “mobiledevice” can be used synonymously herein.

Examples of a UE (e.g. UE 110 a or 110 b) may include a cellular phone,personal data assistant (PDA), smart phone, laptop, tablet personalcomputer (PC), pager, portable computer, portable gaming device,wearable electronic device, or other mobile communications device havingcomponents for communicating voice or data via a mobile communicationnetwork. Other examples include, but are not limited to, a television, aremote controller, a set-top box, a computer monitor, a computer(including a tablet, a desktop computer, a handheld or laptop computer,a netbook computer), a microwave, a refrigerator, a stereo system, acassette player or recorder, a DVD player or recorder, a CD player orrecorder, a VCR, an MP3 player, a radio, a camcorder, a camera, adigital camera, a portable memory chip, a washer, a dryer, awasher/dryer, a copier, a facsimile machine, a scanner, amulti-functional peripheral device, a wristwatch, a clock, and a gamedevice, etc. The UE may include a device and a removable memory module,such as a Universal Integrated Circuit Card (UICC) that includes aSubscriber Identity Module (SIM) application, a Universal SubscriberIdentity Module (USIM) application, or a Removable User Identity Module(R-UIM) application. Alternatively, the UE may include the devicewithout such a module.

FIG. 2 is a schematic illustrating an example network node 200. Asmentioned with regard to FIG. 1, the example network node 200 may be anexample of the eNodeB 105 of the cellular network 120 or the AP 125 ofthe WLAN network 130. The network node 200 can transmit and receivesignals to one or more user equipment based on various communicationprotocols. As an example, the network node 200, as an eNodeB of an LTEnetwork, can support and implement LTE protocols. As another example,the network node 200 can support and implement IEEE 802. 11 protocols asan AP for a WLAN network. The example network node 200 includes aprocessing module 202, a wired communication subsystem 204, and awireless communication subsystem 206. The processing module 202 caninclude one or more processing components (alternatively referred to as“processors” or “central processing units” (CPUs)) operable to executeinstructions associated with one or more of the processes, steps, oractions described above in connection with one or more of theimplementations disclosed herein (for example, the operations describedwith respect to FIG. 4). The processing module 202 can also includeother auxiliary components, such as random access memory (RAM), readonly memory (ROM), or secondary storage (for example, a hard disk driveor flash memory). The processing module 202 can execute certaininstructions and commands to provide wireless or wired communication,using the wired communication subsystem 204 or a wireless communicationsubsystem 206. A skilled artisan will readily appreciate that variousother components can also be included in the example network node 200.

FIG. 3 is a schematic illustrating an example UE 300. As mentioned withregard to FIG. 1, the UE 300 may be an example of the UE 110 a or 110 b. In some instances, the UE 300 can communicate with one or morecommunication networks that embody different communication standards orprotocols. For example, the UE 300 may communicate with both an LTEnetwork and a WLAN network. The example UE 300 includes a processingunit 302, a computer readable storage medium 304 (for example, ROM orflash memory), a wireless communication subsystem 306, an interface 308,and an I/O interface 310. Similar to the processing module 202 of FIG.2, the processing unit 302 can include one or more processing components(alternatively referred to as “processors” or “central processing units”(CPUs)) configured to execute instructions related to one or more of theprocesses, steps, or actions described above in connection with one ormore of the implementations disclosed herein (for example, operationsdescribed with respect to FIG. 4). The wireless communication subsystem306 may be configured to provide wireless communications for datainformation or control information provided by the processing unit 302.The wireless communication subsystem 306 can include, for example, oneor more antennas, a receiver, a transmitter, a local oscillator, amixer, and a digital signal processing (DSP) unit. In some embodiments,the wireless communication subsystem 306 can support advanced multi-userdetection (MUD) receivers and multiple input multiple output (MIMO)transmissions.

In some implementations, the wireless communication subsystem 306 caninclude multiple subsystems. As an example, the wireless communicationsubsystem 306 can include an LTE subsystem and a WLAN subsystem thatsupport communications based on LTE and WLAN standards, respectively. Insome implementations, each of the subsystem can include, for example, areceiver, a transmitter, or any other appropriate components. Thetransmitter can include any appropriate processor, memory, or othercircuitry for performing data transmission while the receiver caninclude any appropriate processor, memory, or other circuitry forperforming data reception. In some implementations, an LTE subsystem caninclude an LTE transmitter and an LTE receiver that are configured totransmit and receive data based on the LTE standard. Similarly, a WLANsubsystem can include a WLAN transmitter and a WLAN receiver that areconfigured to transmit and receive data based on the WLAN standard. Insome implementations, the transmitters and receivers can include one ormore processors that are operable to perform, for example, operationsdescribed with respect to FIG. 4, in addition to or as an alternative tooperations specified by the LTE, WLAN, or other standards or protocols.

The interface 308 can include, for example, one or more of a screen ortouch screen (for example, a liquid crystal display (LCD), a lightemitting display (LED), an organic light emitting display (OLED), amicroelectromechanical system (MEMS) display), a keyboard or keypad, atrackball, a speaker, and a microphone. The I/O interface 310 caninclude, for example, a universal serial bus (USB) interface. A skilledartisan will readily appreciate that various other components can alsobe included in the example UE device 300.

FIG. 4 is a flowchart illustrating an example process 400 fortransmission power and rate control of a WLAN transmitter. In someimplementations, the example process 400 can be performed, for example,by the WLAN transmitter, to allow concurrent operations of LTE and WLANtransceivers and to mitigate interference from the WLAN transmission toan LTE receiver. The WLAN transmitter can be a transmitter that iscapable of data transmission based on a WLAN standard or protocol. TheWLAN transmitter can be located within or associated with userequipment, a network node. For example, the WLAN transmitter can be thetransmitter of the WLAN transceiver 115 of the UE 110 b, or it can be atransmitter within the AP 125 of the WLAN network 130 in FIG. 1.

In some implementations, the example process 400 shown in FIG. 4 can bemodified or reconfigured to include additional, fewer, or differentoperations, which can be performed in the order shown or in a differentorder. In some instances, one or more of the operations can be repeatedor iterated, for example, until a terminating condition is reached. Insome implementations, one or more of the individual operations shown inFIG. 4 can be executed as multiple separate operations, or one or moresubsets of the operations shown in FIG. 4 can be combined and executedas a single operation.

At step 410, an LTE RX de-sense value is determined. The LTE RX de-sensecan be a function of the operating WLAN channel, the operating LTEchannel, the WLAN TX power, and any other appropriate parameters. Insome implementations, the LTE_RX_desense value can be a known quantitythat is characterized offline and stored in an ini or config file, or inanother format. Given the operating conditions (e.g., operatingchannels, TX power), the LTE RX de-sense value can be identified, forexample, by looking up in the ini or config file or another source. Insome other implementations, the LTE RX de-sense value can be calculatedor updated online during the operation of the WLAN receiver.

In some instances, the LTE RX de-sense value reacts linearly to WLAN TXpower reduction. For example, a 1 dB reduction in WLAN TX power canresult in 1 dB decrease in the LTE RX de-sense value. In someimplementations, a lookup table or a function may be used to capture therelationship between the LTE RX de-sense value and the WLAN TX powerreduction.

At step 412, the WLAN TX power (e.g., WL_TRGT_PWR) can be determined. Asan example, the WLAN TX power can be determined based on the LTE RXde-sense value according to Equation (1):

WL_TRGT_PWR=WL_CURRENT PWR_LTE_RX_DESNSE   (1).

The WL_TRGT_PWR can represent the target or desired TX power of the WLANtransmitter such that concurrent operations of the LTE and WLANtransceivers are allowed without LTE receiver de-sensing. TheWL_CURRENT_PWR can represent another (or a current) TX power withoutconcurrent LTE and WLAN operations. In some instances, the WLAN TX powerand the LTE RX de-sense value may be related in another manner than theEquation (1). In some instances, the reduced WL_TRGT_PWR can cause areduced SINR in the UL direction at a remote WLAN receiver. In theexample shown in FIG. 1, when the WLAN transceiver 115 of the UE 110 bis transmitting data in the UL direction (e.g., from the UE 100 b to theAP 125) using a reduced TX power, the received SINR at the AP 125 may bedecreased.

At step 420, a received signal strength threshold can be calculated. Forexample, the received signal strength threshold can be a low signalstrength threshold that indicates a minimum required received signalstrength at a WLAN receiver. In some instances, the received signalstrength threshold can be represented by LO_RSSI (low received signalstrength indicator). In some implementations, the WLAN receivers at bothends of the uplink and downlink can have symmetric receiver sensitivity.The LO_RSSI can be calculated, for example, according to Equation (2):

LO_RSSI=REG_RSSI-LTE_RX_DESNSE   (2).

The REG_RSSI (regular received signal strength indicator) can representreceived signal strength at the WLAN receiver during regular operationswithout concurrent LTE and WLAN operations. For instance, the REG_RSSImay be the received signal strength measured at a WLAN receiver when thecorresponding WLAN transmitter is transmitting using WL_CURRENT_PWR. TheRSSI can be symmetric at both ends of the link. In some cases, if theRSSI is not symmetric at both ends of the link, a lower bound of theREG_RSSI can be used as the REG_RSSI in Equation (2). The lower bound ofthe REG_RSSI can be, for example, a corresponding WLAN receiversensitivity when the WLAN transmitter is transmitting usingWL_CURRENT_PWR, or another lower bound. In some implementations,additional or different approaches can be used to determine the receivedsignal strength threshold LO_RSSI based on the LTE_RX_DESENSE value.

At step 430, a transmission rate of the WLAN transmitter is determined.In some instances, the transmission rate can be used to accommodate theTX power reduction and to allow for concurrent LTE and WLAN operations.In some implementations, the transmission rate can be referred to as anew transmission rate (i.e., NEW_WL_RATE), compared with an old orcurrent transmission rate (i.e., OLD_WL_RATE) used when the WLANtransmitter does not perform concurrent LTE and WLAN operations. The NEWWL_RATE can be determined so that it requires a receiver sensitivityless than or equal to the LO_RSSI determined at step 420. In someinstances, a highest transmission rate with required receiversensitivity less than the LO_RSSI can be selected as the NEW_WL_RATE. Insome implementations, a look-up table or a function that maps atransmission rate and required receiver sensitivity can be pre-computed,stored or otherwise made available to the WLAN transmitter. TheNEW_WL_RATE may be looked up, computed, updated, or otherwise determinedbased on the received signal strength threshold LO_RSSI.

In some implementations, an aggressive approach can choose, for example,the highest rate where the required receiver sensitivity based onLO_RSSI where the LO_RSSI is determined according to Equation (2) withREG_RSSI being the received signal strength measured at a WLAN receiverwhen the corresponding WLAN transmitter is transmitting usingWL_CURRENT_PWR. In some other implementations, a conservative approachcan choose, for example, the highest rate where the required receiversensitivity less than LO_RSSI according to Equation (2) with REG_RSSIbeing a corresponding WLAN receiver sensitivity when the WLANtransmitter is transmitting using WL_CURRENT_PWR. Additional ordifferent factors can be taken into account in determining theNEW_WL_RATE.

At step 440, whether a new transmission rate is found can be determined.In some instances, for example, the LO_RSSI (e.g., due TX powerreduction) may be so low that no viable transmission rate can besupported. In this case, no NEW_WL_RATE is found. Upon such adetermination, the WLAN transmitter may, at step 450, transmit with thecurrent or old rate (OLD_WL_RATE) during the LTE TX period (e.g., duringLTE UL frame duration) but not during the LTE RX period. Otherwise, if aNEW_WL_RATE is found, a throughput comparison (between using NEW_WL_RATEand OLD_WL_RATE) can be performed at step 470 to decide whattransmission rate to be used.

At step 415, a frame aggregation size can be determined based on acurrent transmission rate (e.g., OLD_WL_RATE). The OLD_WL_RATE can bethe transmission rate of the WLAN transmitter without concurrent LTE andWLAN operations, the transmission rate when the WLAN transmitter istransmitting using WL_CURRENT_PWR, or another transmission rate. In someimplementations, the WLAN transceiver can support, for example, IEEE802.11n and 802.11ac that allows frame aggregation. (It is understoodthat IEEE 802.11ac operates in 6 GHz, but if intermodulation or othernon-direct interference with a TDD radio occurs, then the exampletechniques can be applicable.) In WLAN and LTE coexistence scenarios,with extended LTE DL durations or frequent UL/DL transitions, the use ofWLAN frame aggregation can be inhibited. Therefore, it may be doublyadvantageous to operate continuously at lower rates (e.g., usingNEW_WL_RATE) rather than operating intermittently at higher rates (e.g.,using NEW_WL_RATE).

Table 2 shows example LTE TDD frame configurations with thecorresponding UL/DL duty cycles. The LTE TDD frame configuration can beset by the eNB. It can be a known quantity and may not changefrequently. The WLAN transceiver can receive the LTE TDD frameconfiguration information (e.g., the uplink-downlink configuration indexas shown in the first column of Table 2), for example, via theinterfaces (e.g., interfaces 116 in FIG. 1) between the LTE transceiverand the WLAN transceiver. In some instances, the LTE TDD frameconfiguration can be exchanged over the BT-Sig 2 interface, rather thanrelying on the 3-wire (e.g., LTE_TX, LTE_RX_WLAN PRIO) interfaces.

TABLE 2 LTE TDD frame configurations DOWNLINK UPLINK- TO UPLINK DOWNLINKSWITCH CONFIGURATION PERIODICITY 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U DS U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms  DS U U U D D D D D 4 10 ms  D S U U D D D D D D 5 10 ms  D S U D D D D DD D 6 5 ms D S U U U D S U U D D is a subframe for downlink transmissionS is a “special” subframe used for a guard time U is a subframe foruplink transmission

In some implementations, based on the LTE TDD frame configuration, amaximum aggregation size for the OLD_WL_RATE can be determined. Forexample, the maximum aggregation size can be determined such that anaggregated WLAN frame of the maximum aggregation size fit within the LTETX period (e.g., the LTE UL frame duration). In some instances, themaximum aggregation size can depend on other factor such as the devicecapabilities (e.g., available buffers, transmission load, etc.). TheWLAN transmitter can choose an appropriate frame aggregation size lessthan or equal to the maximum frame aggregation size for datatransmission. A frame aggregation size can correspond to certaintransmission efficiency, which can further determine a transmissionthroughput.

FIG. 5 is a plot 500 illustrating example transmission efficienciesversus different aggregation sizes. Specifically, curves 510 and 520represent example simulation and theoretical UDP utilizations, whilecurves 530 and 540 represent example simulation and theoretical TCPutilizations with respect to the different frame aggregation size asshown on the x-axis. Given a frame aggregation size, a correspondingefficiency or utilization can be determined according to one or more ofthe utilization curves. For example, given a frame aggregation size of36, its corresponding transmission efficiency can be determined to beabout 80%, according to the TCP theoretical utilization curve 540.Additional or different efficiency curves can be used for determiningthe transmission efficiency. In some implementations, in addition to oras an alternative to the transmission efficiency or utilization curves,a look-up table, a function, or another algorithm can be used todetermine the transmission efficiency given an aggregation size.

At step 425, a throughput (TP1) corresponding to OLD_WL_RATE can beestimated or otherwise determined based on the aggregation size and thecorresponding efficiency. For example, the throughput TP1 can beestimated based on Equation (3):

TP1=OLD_WL_RATE×Efficiency   (3).

The throughput can take into consideration other factors and may bedetermined in another manner based on the aggregation size and theefficiency.

At step 460, a throughput (TP2) corresponding to NEW_WL_RATE can beestimated or otherwise determined. The TP2 can be determined similarlyto the TP1, or it can be determined in a different manner. For example,the throughput TP1 can be estimated based on Equation (4):

TP2=NEW_WL_RATE×Efficiency   (4).

Here, the efficiency corresponds to the efficiency using NEW_WL_RATE.The efficiency can be determined, for example, based on a frameaggregation size for NEW_WL_RATE. The efficiency can be determined basedon the example techniques described for determining the efficiency usingOLD_WL_RATE (e.g., according to an efficiency curve, function, look-uptable, etc.), or another technique. In some instances, to determine theefficiency using NEW_WL_RATE, the maximum frame aggregation size forNEW_WL_RATE needs to be determined. In some implementations, the maximumframe aggregation size for the OLD_WL_RATE can be used as the maximumframe aggregation size for the NEW_WL RATE, or the maximum frameaggregation size for the OLD_WL_RATE can be modified (e.g.,adding/subtracting a constant, multiplying a scalar, etc.) to determinethe maximum frame aggregation size for the NEW_WL RATE.

In some implementations, the maximum frame aggregation size forNEW_WL_RATE can be determined based on the LTE TDD frame configurationand the NEW_WL_RATE. For instance, the maximum frame aggregation sizefor the NEW_WL_RATE can be determined such that the aggregated WLANframe can be transmitted during the whole LTE TDD frame time using theNEW_WL_RATE, thus allowing concurrent LTE and WLAN operations. Themaximum frame aggregation size for the NEW_WL_RATE can depend on otherfactors such as device capabilities. In some implementations forNEW_WL_RATE, the maximum allowable aggregation size can be used toidentify the corresponding efficiency and then estimate or otherwisedetermine the throughput TP2 for the NEW_WL_RATE.

At step 470, the throughput TP2 for the NEW_WL_RATE and the throughputTP1 for the OLD_WL_RATE can be compared. In some instances, if TP2 isless than TP1, the WLAN transmitter can continue to transmit using theOLD_WL_RATE during LTE TX period as indicated by step 450. On the otherhand, if TP2 is larger than or equal to TP1, the WLAN transmitter canadopt the NEW_WL_RATE for data transmission.

At step 490, data can be transmitted using the WL_TRGT_PWR andNEW_WL_RATE during the whole LTE TDD frame time. In this case, inaddition to transmitting during LTE TX period (e.g., one or more LTE ULsubframes), the WLAN transmitter can also transmit during LTE RX period(e.g., one or more LTE DL subframes), and thus achieving concurrentoperations of the WLAN transceiver and LTE transceiver.

While several implementations have been provided in the presentdisclosure, it should be understood that the disclosed systems andmethods may be embodied in many other specific forms without departingfrom the scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various implementations as discrete or separate maybe combined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

While the above detailed description has shown, described, and pointedout the fundamental novel features of the disclosure as applied tovarious implementations, it will be understood that various omissionsand substitutions and changes in the form and details of the systemillustrated may be made by those skilled in the art, without departingfrom the intent of the disclosure. In addition, the order of methodsteps are not implied by the order they appear in the claims.

What is claimed is:
 1. A method performed at a wireless local areanetwork (WLAN) transmitter of a communication system in response tointerference with a long term evolution (LTE) receiver, the methodcomprising: determining a de-sense value of the LTE receiver;determining a transmission rate for the WLAN transmitter, thetransmission rate requiring an equal or lower receiver sensitivity thana received signal strength threshold; determining a frame aggregationsize based on the transmission rate and an LTE frame configuration forthe LTE receiver; determining a transmission power based on the de-sensevalue; and transmitting data during a downlink receiving period of theLTE receiver using the transmission rate, the frame aggregation size,and the transmission power.
 2. The method of claim 1, wherein thereceived signal strength threshold is determined based on a differencebetween received signal strength measured at a WLAN receiver and thede-sense value of the LTE receiver.
 3. The method of claim 1, whereinthe received signal strength threshold is determined based on adifference between a second required receiver sensitivity of a secondtransmission rate of the WLAN transmitter and the de-sense value of theLTE receiver.
 4. The method of claim 1, wherein the LTE frameconfiguration comprises an LTE time division duplex (TDD) frameconfiguration and transmitting data comprises transmitting data duringan entire LTE TDD frame of the LTE receiver using the transmission rate,the frame aggregation size, and the transmission power.
 5. The method ofclaim 1, wherein the LTE frame configuration for the LTE receiver isreceived over an interface between the WLAN transmitter and the LTEreceiver.
 6. The method of claim 1, wherein the transmission rate is afirst transmission rate and the frame aggregation size is a first frameaggregation size, the method comprising: determining a first efficiencybased on the first frame aggregation size; determining a firstthroughput based on the first transmission rate and the firstefficiency; determining a second frame aggregation size based on asecond transmission rate and the LTE frame configuration for the LTEreceiver; determining a second efficiency based on the second frameaggregation size; determining a second throughput based on the secondtransmission rate and the second efficiency; and wherein transmittingdata during the downlink receiving period of the LTE receiver using thefirst transmission rate, the first frame aggregation size, and thetransmission power comprises transmitting data during the downlinkreceiving period of the LTE receiver using the first transmission rate,the first frame aggregation size, and the transmission power only if thefirst throughput is larger than the second throughput.
 7. The method ofclaim 6, wherein determining the second frame aggregation size comprisedetermining a maximum frame aggregation size that can be transmittedduring an LTE uplink transmission period using the second transmissionrate.
 8. The method of claim 6, wherein determining the first frameaggregation size comprise determining a maximum frame aggregation sizethat can be transmitted during an entire LTE TDD frame time using thefirst transmission rate.
 9. An apparatus of a communication network,comprising: a long term evolution (LTE) receiver; and a wireless localarea network (WLAN) transmitter, the WLAN transmitter configured to:determine a de-sense value of the LTE receiver; determine a transmissionrate for the WLAN transmitter, the transmission rate requiring an equalor lower receiver sensitivity than a received signal strength threshold;determine a frame aggregation size based on the transmission rate and anLTE frame configuration for the LTE receiver; determine a transmissionpower based on the de-sense value; and transmit data during a downlinkreceiving period of the LTE receiver using the transmission rate, theframe aggregation size, and the transmission power.
 10. The apparatus ofclaim 9, wherein the received signal strength threshold is determinedbased on a difference between received signal strength measured at aWLAN receiver and the de-sense value of the LTE receiver.
 11. Theapparatus of claim 9, wherein the received signal strength threshold isdetermined based on a difference between a second required receiversensitivity of a second transmission rate of the WLAN transmitter andthe de-sense value of the LTE receiver.
 12. The apparatus of claim 9,wherein the LTE frame configuration comprises an LTE time divisionduplex (TDD) frame configuration and the WLAN transmitter is configuredto transmit data during an entire LTE TDD frame of the LTE receiverusing the transmission rate, the frame aggregation size, and thetransmission power.
 13. The apparatus of claim 9, wherein thetransmission rate is a first transmission rate and the frame aggregationsize is a first frame aggregation size, and the WLAN transmitter isconfigured to: determine a first efficiency based on the first frameaggregation size; determine a first throughput based on the firsttransmission rate and the first efficiency; determine a second frameaggregation size based on a second transmission rate and the LTE frameconfiguration for the LTE receiver; determine a second efficiency basedon the second frame aggregation size; determine a second throughputbased on the second transmission rate and the second efficiency; andwherein the WLAN transmitter is configured to transmit data during thedownlink receiving period of the LTE receiver using the firsttransmission rate, the first frame aggregation size, and thetransmission power only if the first throughput is larger than thesecond throughput.
 14. The apparatus of claim 9, wherein the WLANtransmitter is configured to receive the LTE frame configuration over aninterface between the WLAN transmitter and the LTE receiver.
 15. Anon-transitory computer-readable medium storing instructions that areoperable when executed by data processing apparatus to performoperations at a first wireless devices in response to interference witha long term evolution (LTE) receiver, the operations comprising:determining a de-sense value of the LTE receiver; determining atransmission rate for the WLAN transmitter, the transmission raterequiring an equal or lower receiver sensitivity than a received signalstrength threshold; determining a frame aggregation size based on thetransmission rate and an LTE frame configuration for the LTE receiver;determining a transmission power based on the de-sense value; andtransmitting data during a downlink receiving period of the LTE receiverusing the transmission rate, the frame aggregation size, and thetransmission power.
 16. The computer-readable medium of claim 15,wherein the received signal strength threshold is determined based on adifference between received signal strength measured at a WLAN receiverand the de-sense value of the LTE receiver.
 17. The computer-readablemedium of claim 15, wherein the received signal strength threshold isdetermined based on a difference between a second required receiversensitivity of a second transmission rate of the WLAN transmitter andthe de-sense value of the LTE receiver.
 18. The computer-readable mediumof claim 15, wherein the LTE frame configuration comprises an LTE timedivision duplex (TDD) frame configuration and transmitting datacomprises transmitting data during an entire LTE TDD frame of the LTEreceiver using the transmission rate, the frame aggregation size, andthe transmission power.
 19. The computer-readable medium of claim 15,wherein the transmission rate is a first transmission rate and the frameaggregation size is a first frame aggregation size, the operationscomprising: determining a first efficiency based on the first frameaggregation size; determining a first throughput based on the firsttransmission rate and the first efficiency; determining a second frameaggregation size based on a second transmission rate and the LTE frameconfiguration for the LTE receiver; determining a second efficiencybased on the second frame aggregation size; determining a secondthroughput based on the second transmission rate and the secondefficiency; and wherein transmitting data during the downlink receivingperiod of the LTE receiver using the first transmission rate, the firstframe aggregation size, and the transmission power comprisestransmitting data during the downlink receiving period of the LTEreceiver using the first transmission rate, the first frame aggregationsize, and the transmission power only if the first throughput is largerthan the second throughput.
 20. The computer-readable medium of claim19, wherein determining the first frame aggregation size comprisedetermining a maximum frame aggregation size that can be transmittedduring an entire LTE TDD frame time using the first transmission rate.